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Special Radial DrilL

esting example is shewn in Fig. 291, designed by Messrs. Geo.
Booth & Co. for performing a variety of operations. The circular
table A, provided with worm wheel B, may be revolved whenever
the worm shaft c is connected to the driving shaft D by belt; at
other times it is stationary. A bracket E? fixed upon the bed of
the machine, carries a tool F through the medium of the two
slides G and H, each provided with hand wheel and screw, thus
giving adjustment in both directions. When, therefore, a boiler end
plate is fastened to the table through temporary rivet holes, and
the worm gear connected up, the tool F serves to turn the outer
edge, the usual back gear being seen at K. The power further
passes through mitre wheels and vertical shaft within the pillar to
the spur wheels L M, and thence through shafts N and o to the
drill spindle, the feed motions being as previously described
The simple drilling done on this machine is the taking out of
tube holes in the manner shewn at B, Fig, 169; but large flue
holes are made by using the head p and three cutter bars Q Q
held by set screws with removable cutters, forming in fact a large
pin drill. In all cases a hole is first drilled in the plate to receive
the ' pin' and steady the cutter, and the radial arm R being long
may be fixed to the bracket s when doing heavy work. But the
most interesting feature to the student is the method by which
large oval holes may be formed, such as those required as man-
holes. A short vertical shaft T is connected to the driving shaft
N by gearing of 2 to i, the same ratio as that of the bevel gear at
u. At the lower end of T is an eccentric stud adjustable within
certain limits, and a rod v connects this with the saddle. The
shaft T making its revolution in the same time as the drill spindle,
an inspection of the diagram at w shews that the cutter will be
compelled, by the movement of the saddle, to mark out a true
ellipse instead of the circle it commenced with, which will be
understood by comparing the numbers; of course only one cutter
bar can be used. The tube j may be turned ,rpund within the
base x, for fine adjustment, by, the worm gear at Y, but the
position of the arm R is first roughly obtained by releasing the
bolts zz. The lifting is effected by tlje $crew a, driven from the
central vertical shaft by spur wheelsr at ^, reversed or put out of
gear at will by the htndle d mqvefl, horizpr|tally. This machine